The invention relates to a method of treating parts of an underground permeable formation surrounding a well penetrating the formation which is producing sand or is likely to produce said during the lifetime of the well. More particularly, the invention relates to a method of treating formation parts having the pore spaces thereof substantially filled with gas and having water adhering to the walls of the pore spaces. In its more specific aspects the invention is concerned with the consolidation of a gas-containing formation without impairing the permeability thereof to an extent that would reduce the valve of the well penetrating said formation as a production well.
There exist numerous undergound formations from which gases, such as hydrocarbon gases are being recovered via wells penetrating such formations. In case the formation parts surrounding a well consist of formation grains that are insufficiently bonded together, large amounts of such grains will be detached from the formation by the gas flowing from the pore spaces into the well and hamper the recovery of gas through the well. Several types of treatments that are aimed at consolidating or improving the consolidation of the formation parts surrounding production wells have been suggested and tried out in the past. However, it became clear that although these methods often proved successful in improving the consolidation of incompetent formation areas having the pore space thereof filled with liquid such as crude oil, these methods when applied to gas-filled formations are apt to impair the permeability of the formation pore spaces by liquid blocking.
The application of halides of silicon for plugging purposes in the pore space around wells has been known for a long time. Silicon chloride dissolved in oil and silicon fluoride in vapor phase have been injected into water-filled layers that have to be shut off.
Also, the use of halides of silicon dissolved in nonaqueous liquids is known for consolidating water-wet oil-containing formation parts. Application, however, of his known technique in a water-wet gas-containing formation would however, seriously impair the permeability thereof since the nonaqueous liquid left in the pore space cannot fully be removed therefrom after the treatment. In general, it can be said that application of liquids in a gas well for treatment purposes is not considered attractive since it will often lead to productivity impairment of the well due to the inability of the well to clean itself, when placed on production, of the liquids which have invaded the formation during the treatment. This so-called liquid-blocking of the pore space is a serious disadvantage of the known treatments designed for consolidating the formation around gas wells.
Descriptions of such prior plugging and consolidating uses of halides of silicon are contained in patents such as the following:
__________________________________________________________________________ U.S. Patent Specification Reagent Carrier Water Present Formation Object __________________________________________________________________________ 3,087,542 SiF.sub.4 Gas In thief stone Gas Plugging of thief zones 3,252,513 SiCl.sub.4 Oil Pre-injected Calcareous Plugging 3,055,426 Silicon Oil Yes Oil/Gas Consolidation halide 2,808,886 SiCl.sub.4 Wet Gas Oil Plugging 3,055,425 Silicon Liquid Yes Oil/Gas Consolidation+ halide stabilization 3,090,435 " Liquid Yes Consolidation 3,070,161 " Oil Connate Oil Consolidation+ Stabilization 2,019,908 " Oil do Oil Plugging or Consolidation __________________________________________________________________________
Object of the invention is a treatment method for improving the strength of an incompetent gas-containing formation without impairing the permeability thereof to an extent that would render the wells through which such treatment has been carried out incapable for the recovery of gas therefrom at economic production rates.
A further object of the invention is a cheap treatment for consolidating a gas-containing formation in the zone thereof that surrounds a well penetrating said formation, which treatment is moreover simple and can be carried out with a minimum of equipment.